code: def sphinx_show(html_dir):
      index_html = op.join(html_dir, "index.html")
      if not op.isfile(index_html):
          sys.exit("Cannot show pages, build the html first.")
      import webbrowser
  
      webbrowser.open_new_tab(index_html)
  
file_path: imageio/tasks/docs.py
imports: import os
  import sys
  import os.path
  import shutil
  from invoke import task
  from ._config import DOC_DIR, DOC_BUILD_DIR
label_desc: Use image node_id 4 for calling a global function with example usage: sphinx_show(html_dir) without return types